Compatibility study between sitagliptin and pharmaceutical excipients used in solid dosage forms

Differential scanning calorimetry (DSC) is a primary technique for measuring the thermal properties of materials, which reflects the physico-chemical properties of drug substances. In the present study, it is used as a screening technique for assessing the compatibility of sitagliptin with some currently employed pharmaceutical excipients. The influence of processing conditions and their effects (simple blending, co-grinding or kneading) on drug stability was evaluated. Sitagliptin showed a sharp endothermic peak at 212.1 A degrees C with an enthalpy change of 131.5 J g(-1) indicating melting of drug. Facile transformation of dehydrated sitagliptin to monohydrate form was observed in some mixtures, disappearance of sharp melting endothermic peak of sitagliptin was observed in some mixtures. On the basis of DSC results, sitagliptin was found to be compatible with micro crystalline cellulose, croscarmellose, and pregelatinized starch. Some excipient interaction was observed with magnesium stearate, ascorbic acid, and citric acid. X-ray diffractometry and FT-IR were used as supportive tools in interpreting the DSC results. Overall, the excipients selected were compatible with the API and the mixtures are stable within the tested conditions. These results would be useful for formulation development of the film coated tablets of sitaglitptin.